Study on the factors influencing the separation characteristics of explosive bolts

Explosive bolts with weakening grooves are widely employed in aerospace, missile separation, and other fields due to their simple structure and high load-bearing capacity. However, the microsecond-level separation time of these bolts poses significant challenges in capturing the entire separation process. To elucidate the failure modes of explosive bolts and understand the factors influencing their separation characteristics, experimental studies were conducted respectively to investigate the effects of charge weight, the location of weakening grooves, and externally constrained conditions on the separation characteristics of explosive bolts. This study determined the critical charge weights required for explosive bolt separation, and the mechanism of interaction between the failure modes of explosive bolts and the area of stress concentration regions was understood by analyzing the variations in material stress and chamber pressure during the separation process. The findings show that the explosive bolt undergoes a tensile-shear composite fracture when the charge weight increases to a certain value. The creation of weakening grooves on the bolt surface can effectively confine the damaged area of the explosive bolts. A high degree of overlap was observed between the stress concentration areas on the separation cross-section of the explosive bolt and the weakening groove segment. Furthermore, the variations in the distance between the right end of the weakening groove and the bottom of the charge chamber significantly affect the separation cross-section state. Building on these findings, a comparative analysis of the separation characteristics of five experimental types with and without externally constrained conditions was conducted. Notably, under constrained conditions, the head structure of each type of bolt fuses with the upper connecting pieces through explosive welding. By comparing the impact area, the reasons for this phenomenon are elucidated. The research results provide a foundation for optimizing the structural design of weakening groove explosive bolts.